Ionospheric Conductance Spatial Distribution During Geomagnetic Field Reversals

The conductivity of the ionosphere is extremely important in geophysical processes and plays a critical role in magnetosphere‐ionosphere‐thermosphere coupling. Understanding its nature is essential to understand the physics of ionospheric electrodynamics. Earth's magnetic field, which varies greatly in geological time scales, is among the main variables involved in ionospheric conductivity. The present field can be approximated by a magnetic dipole that accounts for ~80% of the magnetic field at the Earth's surface, plus multipolar components making up the remaining ~20%. During a polarity transition the field magnitude diminishes to about 10% of its normal value at the expense, most likely, of decreasing the dipolar component and becoming mostly multipolar in nature. The effects of geomagnetic field variations on the spatial structure of Hall and Pedersen conductances are analyzed in the present work considering some possible reversal scenarios. The spatial structure of both conductances changes significantly with sharp spatial gradients. The conductivity peak heights also change, moving to upper heights as expected for weaker field configurations. Key Points Ionospheric conductance spatial structure varies with geomagnetic field secular variation Ionospheric conductance spatial gradients increase for a weaker geomagnetic field For weaker magnetic fields the ionospheric conductivity layer rises to regions of higher electron density